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Hot water at the ready?

Grundfos, not exactly the new water pump kid on the block, has a system which includes a small 110 ac pump, adjustable timer and smallish manifold/thermostatic valve. Pump/timer are installed in the water heater tank area and manifold is installed at bathroom furthest from the water heater.

Timer is set to come on at say, 6 am, moving hot water from the heater tank to/through the 'open' manifold. The manifold allows incoming water to be returned to the heater tank via the cold water side. At 140 F, a thermostatic valve in the manifold snaps shut.

Bathroom now ready for first shave/shower with immediate, hot water. Pump times out in an hour, or so, after everyone has gone to work, but is adjustable.

Advantages: No wasted water while waiting for hot, and no expense running separate 'return' piping from bath back to water heater.

Sounds like a good idea to me. Should also be a near-zero cost to operate, at least during times where the furnace would normally be coming on to maintain house temperature. I wanted to do exactly that same thing years ago, but my idea was to have a back flow prevention valve in the cold water return line, then run the circulating pump from a timer. When entering the bathroom you would push the button once, then the pump would run for an adjustable period of time- maybe 30 seconds or a minute- whatever it takes to have the water quite warm already at the taps.

I also thought to make a heat exchanger of sorts which would have the cold water inlet to the water tank going through it, then all the drain water as well. Even if you ran the hot tap until the water started coming out hot, the draining water would still be warmer than the cold coming in, and you'd get some pre-heating out of it. Then as you continued with the shower etc, you'd get a higher level of pre-heating.

Saw that system (not sure of the make) about 10 or so years ago
at a home/builder show here in Abq. Was tempted since the master
bath is a LOOOOOOOGN way from the heater, but like most other
things never got a rountuit. :-)
...lew...

Water is cheap. What isn't is heating it. If you have a 30' run from the water heater to the shower then you have 30' of water to toss down the drain. That much cold water comes into the water heater and needs to be heated. When you're done, 30' of hot water starts to cool off and hopefully it's cold in the house so the heat isn't wasted.

With a recirculator you have 60' of water that is in the way, and all 60' of it goes back into the heater where it has to be heated (again). Now you have 60' of water cooling off and probably not all of that waste heat is going to be useful.

Then you have the electricity to run the pump, installation costs, maintenance on the pump, electrics, plumbing.

Better to put as much of that 30' of cold water into the coffee maker to make coffee with, I think.

I have often thought about installing a small electric water heater in My master bathroom and hooking the hot water supply to the heater's inlet. I would then only have a small amount of cold water waste and as soon as the hot incoming water reached the small water heater it would shut off fairly soon and just pass hot water through.
I'm reasonably sure that the cost of a small electric water heater is less than adding the recirculating pump and installation and maint. Associated with it.I do realize that the cost of running the water heater would be higher than the cost of running the pump, but not by a great amount given the convenience of nearly instant hot water at the shower and sink.

My younger brother worked for a company that built similar systems, back in the '80's.

The systems he designed were called TIP (tank in pipe) systems. There was no water heater storage tank to speak of, since the water was circulated through the pipes, until it's needed. Then, water was flash heated as needed.

It seemed like a pretty economical system, but the company was sold to some Asians, and the new owners discovered my brother didn't have a college education and sheepskin, so, they canned him...The company went belly up about six months later.

I recall seeing this or a similar unit on one of the high-end DIY shows. Seemed like a good idea. Insulating all the hot water piping that is accessable in un-heated spaces seems like as a good idea as well.